Flutter Http Request 从 JSON 响应中删除重复项

Question

我按照教程 https://www.digitalocean.com/community/tutorials/flutter-flutter-http 制作了一个应用程序，该应用程序向 API 端点发送 get 请求并返回 JSON 响应。

JSON 响应如下所示：

[{"Order":"order1","Driver":"Driver1","Company":"Company1","Address":"Address1"},{"Order":"order2","Driver":"Driver1","Company":"Company2","Address":"Address2"},{"Order":"order3","Driver":"Driver1","Company":"Company3","Address":"Address3"},{"Order":"order4","Driver":"Driver1","Company":"Cpmpany4","Address":"Address4"},{"Order":"order5","Driver":"Driver1","Company":"Company5","Address":"Address5"},{"Order":"order6","Driver":"Driver2","Company":"Company6","Address":"Address6"},{"Order":"order7","Driver":"Driver2","Company":"Company7","Address":"Address7"},{"Order":"order8","Driver":"Driver2","Company":"Company8","Address":"Address8"},{"Order":"order9","Driver":"Driver2","Company":"Company9","Address":"Address9"},{"Order":"order10","Driver":"Driver2","Company":"Company10","Address":"Address10"},{"Order":"ord0439506","Driver":"Driver3","Company":"Company11","Address":"Address11"},{"Order":"ord0439517","Driver":"Driver3","Company":"Company12","Address":"Address12"},{"Order":"ord0439508","Driver":"Driver3","Company":"Company13","Address":"Address13"}]

http_service.dart

class HttpService {
final String postsURL = "https://myapi:8080/getOrders";

Future<List<Post>> getPosts() async {
  Response res = await get(postsURL);

  if (res.statusCode == 200) {
    List<dynamic> body = jsonDecode(res.body);

    List<Post> posts = body
      .map(
        (dynamic item) => Post.fromJson(item),).toList();
      )
      .toList();

    return posts;
  } else {
    throw "Can't get posts.";
  }
 }
}

posts_model.dart

import 'package:flutter/foundation.dart';

class Post {
  final String order;
  final String driver;
  final String company;
  final String address;

Post({
  @required this.order,
  @required this.driver,
  @required this.company,
  @required this.address,
});

factory Post.fromJson(Map<String, dynamic> json) {
  return Post(
    order: json['Order'] as String,
    id: json['Driver'] as String,
    title: json['Company'] as String,
    body: json['Address'] as String,
  );
}
}

posts.dart

 class PostsPage extends StatelessWidget {
     final HttpService httpService = HttpService();


     @override
     Widget build(BuildContext context) {
       return Scaffold(
         appBar: AppBar(
           title: Text("Orders"),
     ),
        body: FutureBuilder(
        future: httpService.getPosts(),
        builder: (BuildContext context, AsyncSnapshot<List<Post>> snapshot){
      if(snapshot.hasData){
        List<Post> posts = snapshot.data;

        return ListView( 
          children: posts
              .map(
                  (Post post) => ListTile(
                    title: Text(post.driver),
                      trailing: Icon(Icons.keyboard_arrow_right),
                  ),
          )
              .toList(),
        );
      }

      return Center(
          child: CircularProgressIndicator());
    },
  ));
}
}

ma​​in.dart

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
      return MaterialApp(
        title: 'HTTP',
        debugShowCheckedModeBanner: false,
        theme: ThemeData(
           primarySwatch: Colors.blue,
     home: PostsPage(),
     );
   }
}

当应用完成对我的 API 的发布请求时，它会将驱动程序显示为

• 驱动程序 1
• 驱动程序 1
• 驱动程序 1
• 驱动程序 1
• 驱动程序 2
• 驱动程序 2
• 驱动程序 2
• 驱动程序 2
• 驱动程序 3
• 驱动程序 3
• 驱动程序 3

我希望视图只显示每个驱动程序一次，因此没有重复

• 驱动程序 1
• 驱动程序 2
• 驱动程序 3

根据研究，大多数人说要将列表变成一个集合，我尝试在 posts.dart 中将 .toSet() 添加到 .toList() 但仍然显示重复项。我已经搞砸了一段时间，但仍然无法弄清楚。任何帮助将不胜感激。

Answer 1

假设您只想要驱动程序的名称，您可以执行类似遍历列表并将名称添加到另一个列表（如果它不存在）的操作

class PostsPage extends StatelessWidget {
     final HttpService httpService = HttpService();

     List<String> getDrivers(List<Post> posts) {
         List<String> res = [];
         posts.forEach((e) => if(!res.contains(e.driver)) res.add(e.driver));

         return res;
      }

     @override
     Widget build(BuildContext context) {
       return Scaffold(
         appBar: AppBar(
           title: Text("Orders"),
     ),
        body: FutureBuilder(
        future: httpService.getPosts(),
        builder: (BuildContext context, AsyncSnapshot<List<Post>> snapshot){
      if(snapshot.hasData){
        List<Post> posts = snapshot.data;
        List<String> drivers = getDrivers(posts);

        return ListView( 
          children: drivers
              .map(
                  (driver) => ListTile(
                    title: Text(driver),
                      trailing: Icon(Icons.keyboard_arrow_right),
                  ),
          )
              .toList(),
        );
      }

      return Center(
          child: CircularProgressIndicator());
    },
  ));
}
}